The present invention relates to pianos, organs, harpsichords and like instruments which have a keyboard for playing the instrument. In particular, the invention is concerned with the assembly of a side arm of the instrument frame and the key bed that supports the keyboard of the instrument.
The side arms and key bed of pianos and the like are connecting structural members which form a front portion of the piano case or frame. The key bed is connected at each end to the respective side arms of the piano and has an upper surface on which the keyboard of the instrument is mounted. Since the key bed supports the keys, their hinges, stops and associated portions of the piano action, any warpage of the bed can interfere with the regulation that establishes identical function aand timing of the keys and their actions with the strings. Warpage may totally prevent operation of the individual keys, and even slight distortions can cause the response to depression of one or more keys to be so significantly degraded that satisfactory performance is impossible.
In my co-pending application Ser. No. 077,150 filed Sept. 19, 1979 and entitled Key Bed For A Piano Or The Like, a laminated key bed construction is disclosed which utilizes outer laminates of sheet metal and an intermediate material such as particleboard or fiberboard. This laminated key bed construction utilizes the high modulus of metal to improve the stiffness of the bed and correspondingly reduce warpage.
The novel structure of my improved bed is not particularly suited to attachment with the side arms of the piano in accordance with prior art techniques. In the prior art the key bed is formed from laminated hard woods and is attached to the side arms by means of toed screws which are driven upwardly through the key bed into the arm as shown in FIG. 5 of this application. Tightening the toed screws causes severe local stressing of the key bed in the region surrounding the screw, and can cause local failure or loosening of the joint which is undesirable. This problem is particularly pronounced in reconstituted wood materials such as the particleboard or fiberboard.
It is accordingly a general objection of the present invention to provide an improved assembly of the side arm and key bed in a piano or like instrument.